US6912667B1 - System and method for communicating fault type and fault location messages - Google Patents
System and method for communicating fault type and fault location messages Download PDFInfo
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- US6912667B1 US6912667B1 US10/094,247 US9424702A US6912667B1 US 6912667 B1 US6912667 B1 US 6912667B1 US 9424702 A US9424702 A US 9424702A US 6912667 B1 US6912667 B1 US 6912667B1
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- ftfl
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- 238000000034 method Methods 0.000 title claims abstract description 43
- 239000000872 buffer Substances 0.000 claims description 57
- 230000003139 buffering effect Effects 0.000 claims 1
- 230000006854 communication Effects 0.000 description 10
- 238000004891 communication Methods 0.000 description 9
- 238000010586 diagram Methods 0.000 description 7
- 238000012545 processing Methods 0.000 description 4
- 238000012544 monitoring process Methods 0.000 description 3
- 230000003287 optical effect Effects 0.000 description 3
- 238000012546 transfer Methods 0.000 description 3
- 238000011144 upstream manufacturing Methods 0.000 description 3
- 230000001360 synchronised effect Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/24—Testing correct operation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/14—Monitoring arrangements
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J2203/00—Aspects of optical multiplex systems other than those covered by H04J14/05 and H04J14/07
- H04J2203/0001—Provisions for broadband connections in integrated services digital network using frames of the Optical Transport Network [OTN] or using synchronous transfer mode [STM], e.g. SONET, SDH
- H04J2203/0057—Operations, administration and maintenance [OAM]
- H04J2203/006—Fault tolerance and recovery
Definitions
- This invention generally relates to digital wrapper format communications and, more particularly, to a system and method for transporting fault type and fault location (FTFL) messages between simplex devices in a network using a digital wrapper format.
- FTFL fault type and fault location
- Digitally wrapped, or multidimensional frame structure communications generally describe information that is sent as a packet without overhead to control the communication process.
- the packet can also include forward error correction (FEC) to recover the payload if the communication is degraded.
- FEC forward error correction
- One example of such a communication is the synchronous optical network (SONET).
- SONET synchronous optical network
- Another example is the digital wrapper format often used in transporting SONET communications.
- the interface node must include two sets of equipment.
- a communication in the first protocol is received at the first set of equipment (processor).
- the message is unwrapped and the payload recovered.
- Synchronization protocols must be established between the equipment set and a second set of equipment (processor).
- the payload can then be received at the second equipment set and repackaged for transmission in a different protocol.
- the G.709 FTFL message is a 256 byte structure that consists of 1 byte per frame for 256 consecutive frames.
- the 256-byte structure is divided into a 128-byte forward message and a 128-byte backward message.
- the receiving device Upon detection of certain error conditions, the receiving device must generate a 128-byte message to be sent upstream.
- the receiving node examines the overhead field and all the received data bits in payload portion of the G.709 frame to determine if this error condition exists. Once the receiving node has determined that the error exists, it must then generate the 128-byte message and inject it into the data stream in the backward direction.
- FIG. 1 is a schematic block diagram of a full-duplex processing node (prior art).
- a G.709 compliant full-duplex processing node When a G.709 compliant full-duplex processing node is built up from a single integrated circuit device, all the communication of the FTFL in the backward direction takes place within that integrated circuit.
- G.709 compliant full-duplex processing nodes can also be built up from two simplex devices, in which case it is no longer possible to communicate the backwards FTFL information within a single integrated circuit.
- Devices designed to receive a G.709 data stream do not normally need to access the received backward fields because they are used for performance monitoring statistics by the receiving integrated circuit, and are then discarded.
- Devices designed to receive a G.709 data stream do not normally need to access the received backward fields because they are used for performance monitoring statistics by the receiving integrated circuit, and are then discarded.
- a system can be built to transfer the backward information in real time with no intervention from user software, and without the loss of any needed information.
- This invention builds upon an overhead drop architecture to facilitate real-time transport of backward information among simplex devices.
- Systems that are built to be compliant to G.709 must communicate certain error fields upstream in the network. These error fields are transmitted in the allocated backward fields in the overhead part of the datastream. These backward fields are processed by the receiving node of a receiver/transmitter pair to determine the condition of the link being used by the transmitter of the pair.
- the invention defines two external signals to facilitate the report capabilities of the received backward errors, specifically, Fault Type and Fault Location (FTFL) messages.
- FTFL Fault Type and Fault Location
- a method for transporting FTFL messages in a G.709 network-connected simplex device.
- the method comprises: receiving messages from a first source in a digital wrapper frame format with overhead bytes in every frame; recovering FTFL information from the received message overhead bytes; and, selectively supplying modified FTFL information for transmit message overhead bytes to the first source.
- recovering FTFL information from the received message overhead bytes includes recovering a 256 byte FTFL message, including a 128-byte forward message and a 128-byte backward message.
- Selectively supplying modified FTFL information for transmit message overhead bytes to the first source includes the substeps of examining the received messages to determine errors; generating a backward message to report the determined errors; overwriting the received backward message with the generated backward message to create the modified FTFL information; and, in response to overwriting the received backward message with the generated backward message, sending a FTFL_status_out signal. Then, the method further comprises: transmitting messages to the first source with the modified FTFL information in response to the FTFL_status_out signal.
- Overwriting the received backward message with the generated backward message to create modified FTFL information includes the substeps of dropping the overhead bytes in the received message; replacing the received FTFL information with the modified FTFL information; and, writing a buffer with the modified FTFL information using write timing signals responsive to the received messages.
- the FTFL_status_out signal is sent when the modified FTFL information has been buffered.
- FIG. 1 is a schematic block diagram of a full-duplex processing node (prior art).
- FIGS. 2 a and 2 b are schematic block diagrams of systems for transporting fault type and fault location (FTFL) messages in a G.709 network.
- FTFL fault type and fault location
- FIGS. 3A and 3B are diagrams illustrating the G.709 optical channel transport unit (OTU) frame structure.
- FIG. 4 is a flowchart illustrating the present invention method for transporting fault type and fault location (FTFL) messages in a G.709 network-connected simplex device.
- FTFL fault type and fault location
- FIG. 5 is a flowchart illustrating the present invention method for transporting fault type and fault location (FTFL) messages in a G.709 network of connected simplex devices.
- FTFL fault type and fault location
- FIGS. 2 a and 2 b are schematic block diagrams of systems for transporting fault type and fault location (FTFL) messages in a G.709 network.
- the system 200 comprises a simplex processor 202 having an input on line 204 for receiving messages in a digital wrapper frame format with overhead bytes in every frame.
- the simplex processor 202 which is also referred to herein as a simplex device, is an integrated circuit (IC).
- the processor 202 recovers FTFL information from the received message overhead bytes.
- a decoder 206 accepts the received messages and provides decoded messages on line 208 .
- the simplex processor supplies modified FTFL overhead bytes on line 210 .
- messages are encoded again, with either the same, or a modified overhead section, using encoder 212 , and the encoded message is supplied on line 214 .
- FIGS. 3A and 3B are diagrams illustrating the G.709 optical channel transport unit (OTU) frame structure.
- the received FTFL bytes are collected in the receiving processor and are used only to generate performance monitoring statistics within that integrated circuit.
- it is normal to provide read access to all 64 of the G.709 overhead bytes to a user interface during each frame.
- One of these 64 overhead bytes is the FTFL byte for that frame.
- the FTFL byte is shown in row 2 , column 14 of the frame.
- the simplex processor recovers a full FTFL message that includes 128 forward message bytes and 128 backward messages bytes. These FTFL bytes are collected, one byte every frame, over the course of 256 frames. It should be understood that the present invention is not limited to any particular frame or superframe structure.
- the receiving simple processor provides read access to the calculated FTFL bytes instead by overwriting the received FTFL bytes with the calculated FTFL bytes that should be sent upstream.
- this invention defines a signal that is used to identify when the message is present. Then, a simple circuit such as a field programmable gate array is used to transfer these FTFL bytes from one simplex processor to another.
- a buffer 216 is shown having an input connected to line 210 to receive FTFL bytes and an output on line 218 to selectively supply modified FTFL information for transmit message overhead bytes.
- the buffer 216 can be any register or memory device capable of storing a complete FTFL backward message.
- the buffer 216 can be a field programmable gate array (FPGA).
- the transmit message is ultimately sent to the device or node supplying the received message (not shown) on line 204 .
- the simplex processor 202 examines the received messages on line 204 to determine errors, generates a backward message to report the determined errors, and overwrites the received backward message with the generated backward message to create modified FTFL information supplied at the output on line 210 .
- the 128 byte backward message is modified in response to the determined errors.
- the simplex processor 202 maintains the received backward message.
- the term “maintains” as used herein is understood to mean that no modified backward message is written to the buffer 216 . Note that when the backward message is not modified, there is no reason to change the FTFL backward message portion of the transmit message. In some aspects of the system 200 , the backwards message can be dropped into the buffer 216 , even if it is not modified. Alternately, the transmit message can be sent with a default FTFL backwards message.
- the simplex processor 202 also has an output connected to line 220 for sending a FTFL_status_out signal. This signal is sent in response to overwriting the received backward message with the generated backward message in the buffer 216 .
- the system 200 is enabled because the buffer 216 supplies the modified FTFL information in response to the FTFL_status_out signal on line 220 .
- the simplex processor 202 also has an output to supply write timing signals on line 222 .
- the simplex processor 202 drops the overhead bytes from the received message on line 204 , replaces the received FTFL information with the modified FTFL information, and writes modified FTFL information into the buffer 216 using the write timing signals.
- the simplex processor 202 sends the FTFL_status_out signal on line 220 .
- the buffer 216 supplies the modified FTFL information for reading into the transmit message overhead bytes on line 218 using read timing signals on line 224 responsive to the transmit messages.
- the receive message timing is likely to be different than the transmit message timing.
- the buffer 216 supplies one FTFL byte per transmit frame. That is, the buffer receives one read timing signal on line 224 per transmit frame and supplies 1 FTFL byte in response. Alternately, the buffer 216 can supplies the 128-byte backward message in one transmit frame. That is, the buffer can supply the 128 byte backward message in the span of one transmit frame (or one clock cycle) in response to a single read timing signal on line 224 .
- the system 200 is perhaps better appreciated in the context of a G.709 network of connected simplex devices.
- a second simplex processor 240 must be introduced.
- the second simplex processor 240 has an input connected to the buffer output on line 218 , and an output on line 242 for supplying transmit message overhead bytes with the modified FTFL information.
- the second processor 240 typically includes a decoder 244 and an encoder 246 .
- the second simplex processor 240 has an input on line 220 to accept the FTFL_status_out signal.
- the second simplex processor reads the modified FTFL information from the buffer 216 on line 218 in response to receiving the FTFL_status_out signal on line 220 .
- the second simplex processor 240 has an output to supply read timing signals on line 224 .
- the second simplex processor 240 reads the modified FTFL information from the buffer 216 using the read timing signals on line 224 .
- the combination of the buffer 216 , with the FTFL_status_out signal on line 220 permits the FTFL information to be passed between devices that are not necessarily operating with the same clock. It should also be realized that the present invention means for transferring the FTFL information permits the interface between devices to be the simplest form of buffer.
- FIG. 2 b is a schematic block diagram illustrating a G.709 network where the buffer 216 (or two buffers) is used to additionally transport FTFL backward messages from the second simplex processor 240 to the first simplex process 202 .
- the second simplex processor supplies modified backward message bytes to the buffer 216 and uses a FTFL_status_out signal on line 300 to indicate when the buffer is ready.
- the buffer 216 and the FTFL_status_out signals permit the buffer to be loaded at the pace of the first simplex device 202 and unloaded at the pace needed to support the second simplex device 240 .
- the two simplex devices need not be synchronized for the present invention FTFL function.
- FIG. 4 is a flowchart illustrating the present invention method for transporting fault type and fault location (FTFL) messages in a G.709 network-connected simplex device.
- FTFL fault type and fault location
- the method begins at Step 400 .
- Step 402 receives messages from a first source in a digital wrapper frame format with overhead bytes in every frame.
- Step 404 recovers FTFL information from the received message overhead bytes.
- Step 406 selectively supplies modified FTFL information for transmit message overhead bytes to the first source.
- Recovering FTFL information from the received message overhead bytes in Step 404 includes recovering a 256 byte FTFL message, including a 128-byte forward message and a 128-byte backward message.
- selectively supplying modified FTFL information for transmit message overhead bytes to the first source includes substeps.
- Step 406 a examines the received messages to determine errors.
- Step 406 b generates a backward message to report the determined errors.
- Step 406 c overwrites the received backward message with the generated backward message to create the modified FTFL information.
- selectively supplying modified FTFL information for transmit message overhead bytes to the first source includes maintaining (as defined above) the received backward message when there are no errors to report.
- selectively supplying modified FTFL information for transmit message overhead bytes to the first source includes a further substep.
- Step 406 d sends a FTFL_status_out signal.
- Step 408 transmits messages to the first source with the modified FTFL information in response to the FTFL_status_out signal.
- Overwriting the received backward message with the generated backward message to create modified FTFL information includes substeps.
- Step 406 c 1 drops the overhead bytes in the received message.
- Step 406 c 2 replaces the received FTFL information with the modified FTFL information.
- Step 406 c 3 writes a buffer with the modified FTFL information using write timing signals responsive to the received messages.
- Sending the FTFL_status_out signal in Step 406 d includes sending the FTFL_status_out signal when the modified FTFL information has been buffered.
- transmitting messages to the first source with the modified FTFL information in response to the FTFL_status_out signal in Step 408 includes reading the modified FTFL information from the buffer into transmit message using read timing signals responsive to the transmit messages.
- reading the modified FTFL information from the buffer into the transmit messages using read timing signals responsive to the transmit messages in Step 406 c 4 includes reading the entire 128-byte backward message in response to a one read timing signal. Alternately, Step 406 c 4 reads one FTFL byte per transmit frame (one FTFL byte per read timing signal).
- FIG. 5 is a flowchart illustrating the present invention method for transporting fault type and fault location (FTFL) messages in a G.709 network of connected simplex devices.
- the method starts at Step 500 .
- Step 502 receives messages at a first simplex device in a digital wrapper frame format with overhead bytes in every frame.
- Step 504 recovers FTFL information from the received message overhead bytes.
- Step 506 selectively supplies modified FTFL information.
- Step 508 transmits the modified FTFL information in message overhead bytes using a second simplex device.
- Recovering FTFL information from the received message overhead bytes in Step 504 includes recovering a 256 byte message, including a 128-byte forward message and a 128-byte backward message.
- Step 506 Selectively supplying modified FTFL information in Step 506 includes substeps.
- Step 506 a examines the received messages to determine errors.
- Step 506 b generates a backward message to report the determined errors.
- Step 506 c overwrites the received backward message with the generated backward message to create the modified FTFL message.
- reading the modified FTFL information from the buffer into the transmit messages using read timing signals responsive to the transmit messages in Step 408 includes reading the entire 128-byte backward message in response to a one read timing signal. Alternately, Step 408 reads one FTFL byte per transmit frame (one FTFL byte per read timing signal).
- selectively supplying modified FTFL information can also include the first simplex device maintaining the received backward message when there are no errors to report.
- Overwriting the received backward message with the generated backward message to create the modified FTFL message includes further substeps.
- Step 506 c 1 drops the overhead bytes in the received message.
- Step 506 c 2 replaces the received FTFL information with the modified FTFL information.
- Step 506 c 3 writes a buffer with the modified FTFL message using first simplex device read timing signals.
- Sending the FTFL_status_out signal in Step 506 d includes the first simplex device sending the FTFL_status_out signal when the modified FTFL message has been buffered.
- transmitting the modified FTFL information in message overhead bytes using a second simplex device in Step 508 includes reading the modified FTFL message from the buffer using second simplex device read timing signals.
- reading the modified FTFL information from the buffer using second simplex device read timing signals in Step 508 includes reading one FTFL byte per transmit message frame (one FTFL byte per read signal). Alternately, the entire 128-byte backward message is read in one transmit frame (128 bytes per read signal).
- receiving messages at a first simplex device in a digital wrapper frame format with overhead bytes in every frame in Step 502 include receiving messages from a third device.
- Transmitting the modified FTFL information in message overhead bytes using a second simplex device in Step 508 includes transmitting to the third device.
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US10/094,247 US6912667B1 (en) | 2002-03-08 | 2002-03-08 | System and method for communicating fault type and fault location messages |
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Citations (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4970714A (en) * | 1989-01-05 | 1990-11-13 | International Business Machines Corp. | Adaptive data link protocol |
US5130980A (en) * | 1989-11-16 | 1992-07-14 | Fujitsu Limited | Data communication system with protection of error propagation |
US5151902A (en) * | 1989-03-22 | 1992-09-29 | Siemens Aktiengesellschaft | Method and apparatus for quality monitoring of at least two transmission sections of a digital signal transmission link |
US5307353A (en) * | 1990-05-09 | 1994-04-26 | Fujitsu Limited | Fault recovery system of a ring network |
US5422893A (en) * | 1994-08-04 | 1995-06-06 | International Busines Machines Corporation | Maintaining information from a damaged frame by the receiver in a communication link |
US5636203A (en) * | 1995-06-07 | 1997-06-03 | Mci Corporation | Method and system for identifying fault locations in a communications network |
US6145024A (en) * | 1997-06-06 | 2000-11-07 | Hitachi, Ltd. | Input/output optical fiber serial interface link that selectively transfers data in multiplex channel path mode or high speed single channel path mode |
US6298398B1 (en) * | 1998-10-14 | 2001-10-02 | International Business Machines Corporation | Method to provide checking on data transferred through fibre channel adapter cards |
US6310884B1 (en) * | 1998-05-21 | 2001-10-30 | Lsi Logic Corporation | Data transfer method and apparatus that allocate storage based upon a received relative offset |
US20040008988A1 (en) * | 2001-10-01 | 2004-01-15 | Gerstal Ornan A. | Link discovery, verification, and failure isolation in an optical communication system |
-
2002
- 2002-03-08 US US10/094,247 patent/US6912667B1/en not_active Expired - Lifetime
Patent Citations (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4970714A (en) * | 1989-01-05 | 1990-11-13 | International Business Machines Corp. | Adaptive data link protocol |
US5151902A (en) * | 1989-03-22 | 1992-09-29 | Siemens Aktiengesellschaft | Method and apparatus for quality monitoring of at least two transmission sections of a digital signal transmission link |
US5130980A (en) * | 1989-11-16 | 1992-07-14 | Fujitsu Limited | Data communication system with protection of error propagation |
US5307353A (en) * | 1990-05-09 | 1994-04-26 | Fujitsu Limited | Fault recovery system of a ring network |
US5422893A (en) * | 1994-08-04 | 1995-06-06 | International Busines Machines Corporation | Maintaining information from a damaged frame by the receiver in a communication link |
US5636203A (en) * | 1995-06-07 | 1997-06-03 | Mci Corporation | Method and system for identifying fault locations in a communications network |
US6145024A (en) * | 1997-06-06 | 2000-11-07 | Hitachi, Ltd. | Input/output optical fiber serial interface link that selectively transfers data in multiplex channel path mode or high speed single channel path mode |
US6310884B1 (en) * | 1998-05-21 | 2001-10-30 | Lsi Logic Corporation | Data transfer method and apparatus that allocate storage based upon a received relative offset |
US6298398B1 (en) * | 1998-10-14 | 2001-10-02 | International Business Machines Corporation | Method to provide checking on data transferred through fibre channel adapter cards |
US20040008988A1 (en) * | 2001-10-01 | 2004-01-15 | Gerstal Ornan A. | Link discovery, verification, and failure isolation in an optical communication system |
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